Two forms of DNA-dependent RNA polymerase alpha subunit in streptomycetes

Area of Science:

• Microbiology
• Molecular Biology
• Biochemistry

Background:

• Streptomyces granaticolor possesses distinct DNA-dependent RNA polymerase (RNAP) alpha subunits.
• These subunits are crucial for bacterial transcription and gene regulation.

Purpose of the Study:

• To investigate the structural and functional differences of RNAP alpha subunits in Streptomyces granaticolor spores and vegetative cells.
• To elucidate the mechanism behind the observed variations in RNAP alpha subunits.

Main Methods:

• Cloning and sequencing of the RNAP alpha gene from S. granaticolor.
• Overproduction of the RNAP alpha protein in Escherichia coli.
• In vitro proteolytic activity assays using cell-free extracts from spores and vegetative cells.

Main Results:

• Two RNAP alpha subunits (40 kDa and 43 kDa) were identified in S. granaticolor spores; the 43-kDa form was also present in vegetative cells.
• The 40-kDa subunit results from C-terminal truncation of the 43-kDa subunit.
• Spore cell-free extracts demonstrated proteolytic activity targeting the alpha subunit, which was absent in vegetative cell extracts.

Conclusions:

• A novel post-translational modification mechanism involving proteolytic shortening of the RNAP alpha subunit exists in S. granaticolor spores.
• This modification may represent a unique strategy for transcriptional control in Streptomyces species.